Line data Source code
1 : /*
2 : Unix SMB/CIFS implementation.
3 : a async DNS handler
4 : Copyright (C) Andrew Tridgell 1997-1998
5 :
6 : This program is free software; you can redistribute it and/or modify
7 : it under the terms of the GNU General Public License as published by
8 : the Free Software Foundation; either version 3 of the License, or
9 : (at your option) any later version.
10 :
11 : This program is distributed in the hope that it will be useful,
12 : but WITHOUT ANY WARRANTY; without even the implied warranty of
13 : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 : GNU General Public License for more details.
15 :
16 : You should have received a copy of the GNU General Public License
17 : along with this program. If not, see <http://www.gnu.org/licenses/>.
18 : */
19 :
20 : #include "includes.h"
21 : #include "nmbd/nmbd.h"
22 : #include "lib/util/sys_rw_data.h"
23 :
24 : /***************************************************************************
25 : Add a DNS result to the name cache.
26 : ****************************************************************************/
27 :
28 0 : static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
29 : {
30 0 : int name_type = question->name_type;
31 : unstring qname;
32 :
33 0 : pull_ascii_nstring(qname, sizeof(qname), question->name);
34 :
35 0 : if (!addr.s_addr) {
36 : /* add the fail to WINS cache of names. give it 1 hour in the cache */
37 0 : DBG_INFO("add_dns_result: Negative DNS answer for %s\n", qname);
38 0 : add_name_to_subnet( wins_server_subnet, qname, name_type,
39 : NB_ACTIVE, 60*60, DNSFAIL_NAME, 1, &addr );
40 0 : return NULL;
41 : }
42 :
43 : /* add it to our WINS cache of names. give it 2 hours in the cache */
44 0 : DBG_INFO("add_dns_result: DNS gave answer for %s of %s\n", qname, inet_ntoa(addr));
45 :
46 0 : add_name_to_subnet( wins_server_subnet, qname, name_type,
47 : NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr);
48 :
49 0 : return find_name_on_subnet(wins_server_subnet, question, FIND_ANY_NAME);
50 : }
51 :
52 : #ifndef SYNC_DNS
53 :
54 : static int fd_in = -1, fd_out = -1;
55 : static pid_t child_pid = -1;
56 : static int in_dns;
57 :
58 : /* this is the structure that is passed between the parent and child */
59 : struct query_record {
60 : struct nmb_name name;
61 : struct in_addr result;
62 : };
63 :
64 : /* a queue of pending requests waiting to be sent to the DNS child */
65 : static struct packet_struct *dns_queue;
66 :
67 : /* the packet currently being processed by the dns child */
68 : static struct packet_struct *dns_current;
69 :
70 :
71 : /***************************************************************************
72 : return the fd used to gather async dns replies. This is added to the select
73 : loop
74 : ****************************************************************************/
75 :
76 17188 : int asyncdns_fd(void)
77 : {
78 17188 : return fd_in;
79 : }
80 :
81 : /***************************************************************************
82 : handle DNS queries arriving from the parent
83 : ****************************************************************************/
84 0 : static void asyncdns_process(void)
85 : {
86 : struct query_record r;
87 : unstring qname;
88 :
89 0 : debuglevel_set(-1);
90 :
91 0 : while (1) {
92 : NTSTATUS status;
93 :
94 0 : status = read_data_ntstatus(fd_in, (char *)&r, sizeof(r));
95 :
96 0 : if (!NT_STATUS_IS_OK(status)) {
97 0 : break;
98 : }
99 :
100 0 : pull_ascii_nstring( qname, sizeof(qname), r.name.name);
101 0 : r.result.s_addr = interpret_addr(qname);
102 :
103 0 : if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
104 0 : break;
105 : }
106 :
107 0 : _exit(0);
108 : }
109 :
110 : /**************************************************************************** **
111 : catch a sigterm (in the child process - the parent has a different handler
112 : see nmbd.c for details).
113 : We need a separate term handler here so we don't release any
114 : names that our parent is going to release, or overwrite a
115 : WINS db that our parent is going to write.
116 : **************************************************************************** */
117 :
118 0 : static void sig_term(int sig)
119 : {
120 0 : _exit(0);
121 : }
122 :
123 : /***************************************************************************
124 : Called by the parent process when it receives a SIGTERM - also kills the
125 : child so we don't get child async dns processes lying around, causing trouble.
126 : ****************************************************************************/
127 :
128 43 : void kill_async_dns_child(void)
129 : {
130 43 : if (child_pid > 0) {
131 0 : kill(child_pid, SIGTERM);
132 0 : child_pid = -1;
133 : }
134 43 : }
135 :
136 : /***************************************************************************
137 : create a child process to handle DNS lookups
138 : ****************************************************************************/
139 0 : void start_async_dns(struct messaging_context *msg)
140 : {
141 : int fd1[2], fd2[2];
142 : NTSTATUS status;
143 :
144 0 : CatchChild();
145 :
146 0 : if (pipe(fd1) || pipe(fd2)) {
147 0 : DBG_ERR("can't create asyncdns pipes\n");
148 0 : return;
149 : }
150 :
151 0 : child_pid = fork();
152 :
153 0 : if (child_pid) {
154 0 : fd_in = fd1[0];
155 0 : fd_out = fd2[1];
156 0 : close(fd1[1]);
157 0 : close(fd2[0]);
158 0 : DBG_NOTICE("started asyncdns process %d\n", (int)child_pid);
159 0 : return;
160 : }
161 :
162 0 : fd_in = fd2[0];
163 0 : fd_out = fd1[1];
164 :
165 0 : CatchSignal(SIGUSR2, SIG_IGN);
166 0 : CatchSignal(SIGUSR1, SIG_IGN);
167 0 : CatchSignal(SIGHUP, SIG_IGN);
168 0 : CatchSignal(SIGTERM, sig_term);
169 :
170 0 : status = reinit_after_fork(msg, nmbd_event_context(), true);
171 :
172 0 : if (!NT_STATUS_IS_OK(status)) {
173 0 : DBG_ERR("reinit_after_fork() failed\n");
174 0 : smb_panic("reinit_after_fork() failed");
175 : }
176 :
177 0 : asyncdns_process();
178 : }
179 :
180 :
181 : /***************************************************************************
182 : check if a particular name is already being queried
183 : ****************************************************************************/
184 0 : static bool query_current(struct query_record *r)
185 : {
186 0 : return dns_current &&
187 0 : nmb_name_equal(&r->name,
188 0 : &dns_current->packet.nmb.question.question_name);
189 : }
190 :
191 :
192 : /***************************************************************************
193 : write a query to the child process
194 : ****************************************************************************/
195 0 : static bool write_child(struct packet_struct *p)
196 : {
197 : struct query_record r;
198 :
199 0 : r.name = p->packet.nmb.question.question_name;
200 :
201 0 : return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
202 : }
203 :
204 : /***************************************************************************
205 : check the DNS queue
206 : ****************************************************************************/
207 0 : void run_dns_queue(struct messaging_context *msg)
208 : {
209 : struct query_record r;
210 : struct packet_struct *p, *p2;
211 : struct name_record *namerec;
212 : NTSTATUS status;
213 :
214 0 : if (fd_in == -1)
215 0 : return;
216 :
217 0 : if (!process_exists_by_pid(child_pid)) {
218 0 : close(fd_in);
219 0 : close(fd_out);
220 0 : start_async_dns(msg);
221 : }
222 :
223 0 : status = read_data_ntstatus(fd_in, (char *)&r, sizeof(r));
224 :
225 0 : if (!NT_STATUS_IS_OK(status)) {
226 0 : DBG_ERR("read from child failed: %s\n", nt_errstr(status));
227 0 : fd_in = -1;
228 0 : return;
229 : }
230 :
231 0 : namerec = add_dns_result(&r.name, r.result);
232 :
233 0 : if (dns_current) {
234 0 : if (query_current(&r)) {
235 0 : DBG_INFO("DNS calling send_wins_name_query_response\n");
236 0 : in_dns = 1;
237 0 : if(namerec == NULL)
238 0 : send_wins_name_query_response(NAM_ERR, dns_current, NULL);
239 : else
240 0 : send_wins_name_query_response(0,dns_current,namerec);
241 0 : in_dns = 0;
242 : }
243 :
244 0 : dns_current->locked = False;
245 0 : free_packet(dns_current);
246 0 : dns_current = NULL;
247 : }
248 :
249 : /* loop over the whole dns queue looking for entries that
250 : match the result we just got */
251 0 : for (p = dns_queue; p;) {
252 0 : struct nmb_packet *nmb = &p->packet.nmb;
253 0 : struct nmb_name *question = &nmb->question.question_name;
254 :
255 0 : if (nmb_name_equal(question, &r.name)) {
256 0 : DBG_INFO("DNS calling send_wins_name_query_response\n");
257 0 : in_dns = 1;
258 0 : if(namerec == NULL)
259 0 : send_wins_name_query_response(NAM_ERR, p, NULL);
260 : else
261 0 : send_wins_name_query_response(0,p,namerec);
262 0 : in_dns = 0;
263 0 : p->locked = False;
264 :
265 0 : p2 = p->next;
266 0 : DLIST_REMOVE(dns_queue, p);
267 0 : free_packet(p);
268 0 : p = p2;
269 : } else {
270 0 : p = p->next;
271 : }
272 : }
273 :
274 0 : if (dns_queue) {
275 0 : dns_current = dns_queue;
276 0 : DLIST_REMOVE(dns_queue, dns_queue);
277 :
278 0 : if (!write_child(dns_current)) {
279 0 : DBG_NOTICE("failed to send DNS query to child!\n");
280 0 : return;
281 : }
282 : }
283 : }
284 :
285 : /***************************************************************************
286 : queue a DNS query
287 : ****************************************************************************/
288 :
289 0 : bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
290 : {
291 0 : if (in_dns || fd_in == -1)
292 0 : return False;
293 :
294 0 : if (!dns_current) {
295 0 : if (!write_child(p)) {
296 0 : DBG_NOTICE("failed to send DNS query to child!\n");
297 0 : return False;
298 : }
299 0 : dns_current = p;
300 0 : p->locked = True;
301 : } else {
302 0 : p->locked = True;
303 0 : DLIST_ADD(dns_queue, p);
304 : }
305 :
306 0 : DBG_NOTICE("added DNS query for %s\n", nmb_namestr(question));
307 0 : return True;
308 : }
309 :
310 : #else
311 :
312 :
313 : /***************************************************************************
314 : we use this when we can't do async DNS lookups
315 : ****************************************************************************/
316 :
317 : bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
318 : {
319 : struct name_record *namerec = NULL;
320 : struct in_addr dns_ip;
321 : unstring qname;
322 :
323 : pull_ascii_nstring(qname, sizeof(qname), question->name);
324 :
325 : DBG_NOTICE("DNS search for %s -\n", nmb_namestr(question));
326 :
327 : dns_ip.s_addr = interpret_addr(qname);
328 :
329 : namerec = add_dns_result(question, dns_ip);
330 : if(namerec == NULL) {
331 : send_wins_name_query_response(NAM_ERR, p, NULL);
332 : } else {
333 : send_wins_name_query_response(0, p, namerec);
334 : }
335 : return False;
336 : }
337 :
338 : /***************************************************************************
339 : With sync dns there is no child to kill on SIGTERM.
340 : ****************************************************************************/
341 :
342 : void kill_async_dns_child(void)
343 : {
344 : return;
345 : }
346 : #endif
|
